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Ch.14 – History of Life
14.1 – Fossil Evidence of Change
Fossils have been found of organisms
that no longer live on Earth.
Traces (fossils) of modern organisms can
only be dated back to a certain point in
the Earth’s 4.6 billion year history.
Therefore, Life on Earth has changed
(EVOLVED) over the course of the Earth’s
history and continue to do so.
What do we know about fossils and their age?
How/Why do living things change over time?
Ch.14 – History of Life
Fossils
Trace
14.1 – Fossil Evidence of Change
Any evidence of an organism
Replacement
Petrified
Preserved
Mold & Cast
Ch.14 – History of Life
14.1 – Fossil Evidence of Change
Nearly all fossils form in sedimentary rock
because it prevents rapid decomposition
(99% of all living things left no fossils behind)
Ch.14 – History of Life
14.1 – Fossil Evidence of Change
Fossil Dating
Relative Dating
Absolute Dating
Based on the law
of superposition:
newer layers of
rock form on top of
older layers
Radiometric
Dating
-Cannot give exact
age
-Earth’s geology is
constantly shifting
changing the
position of artifacts
Uses the half life
of radioactive
isotopes in order
to determine
specific age.
Ch.14 – History of Life
14.1 – Fossil Evidence of Change
Fossil Dating
Relative Dating
Absolute Dating
Based on the law
of superposition:
newer layers of
rock form on top of
older layers
Radiometric
Dating
-Cannot give exact
age
-Earth’s geology is
constantly shifting
changing the
position of artifacts
Uses the half life
of radioactive
isotopes in order
to determine
specific age.
Ch.14 – History of Life
14.1 – Fossil Evidence of Change
Absolute Dating
U238 decays to Pb206
Half-life – 4.5 billion years
C14 decays to N14
Half-life – 5730 years
Ch.14 – History of Life
14.1 – Fossil Evidence of Change
Geologic Time Scale
Precambrian
4600mya – 542mya
•Earth formed about 4.6 billion years ago
•It took about 500 million years for the crust to form
and for water to start collecting on the surface
•Prokaryotic & eukaryotic unicellular organisms
emerge
•Autotrophic prokaryotes begin to enrich the
atmosphere with O2.
•Multicellular organisms emerge (1st animals)
Ch.14 – History of Life
Paleozoic
14.1 – Fossil Evidence of Change
488mya – 251mya
•Animals diversify
•1st plants
•1st vertebrates
•Life moves out of the oceans
•Insects, amphibians, reptiles scatter
•Ferns & Evergreens cover the Earth
Ch.14 – History of Life
Mesozoic
14.1 – Fossil Evidence of Change
199mya – 65mya
•1st mammals
•Dinosaurs
•Birds
•Gymnosperms (seed-bearing plants) diversify
•Flowering plants appear
•Mass extinction wiped out all dinosaurs, except for
the birds, at the end of the era.
Ch.14 – History of Life
Cenozoic
14.1 – Fossil Evidence of Change
55mya – present
•Mammals diversify and scatter
•Flowering plants scatter
•Primates appear
•Humans create civilizations
and pollution
Ch.14 – History of Life
14.2 – Origin of Life
Origin of Life
Early Ideas Spontaneous Generation
Life arises from non-life
Francisco Reddi 1668
Louis Pasteur mid 1800’s
Biogenesis Life arises from existing life
Ch.14 – History of Life
14.2 – Origin of Life
Origin of Life
Origin Movie
Ch.15 – Evolution
15.1 – Darwin’s Theory of Natural Selection
A new era of biology began on November 24, 1859,
the day Charles Darwin published On the Origin of
Species by Means of Natural Selection
Darwin made two main points in his book:
1. Many current species are descendants of
ancestral species
2. Natural selection is the mechanism for this
evolutionary process
Ch.15 – Evolution
15.1 – Darwin’s Theory of Natural Selection
Darwin’s Influences:
Geologists Hutton and Lyell (late 1700’s) perceived
that changes in Earth’s surface can result from slow
continuous actions still operating today (gradualism)
Thomas Robert Malthus (late 1700’s) hypothesized
that in nature plants and animals produce far more
offspring than can survive, and that Man too is capable
of overproducing if left unchecked
Ch.15 – Evolution
15.1 – Darwin’s Theory of Natural Selection
Darwin’s Observations:
After graduating college Darwin
was accepted on board the
HMS Beagle, which circled the
world from 1831-1836
He observed plant
and animal
adaptations from
many diverse
environments
Ch.15 – Evolution
15.1 – Darwin’s Theory of Natural Selection
Darwin’s most famous observations were of finches
found on the Galapagos Islands off the coast of Ecuador
Many of the islands
had unique climate
& vegetation
Similar looking finches
found on the different
islands had different
adaptations from each
other and were
different from finches
found on the mainland
Ch.15 – Evolution
15.1 – Darwin’s Theory of Natural Selection
Upon return to England Darwin began reflecting on his
observations and started hypothesizing about how
populations change over time.
He did not agree
with French scientist
Jean-Baptiste
Lamarck that living
things changed due
to use and disuse of
certain
characteristics
Ch.15 – Evolution
15.1 – Darwin’s Theory of Natural Selection
With his knowledge of artificial selection – done by
farmers for centuries in order to improve their livestock
or crop populations, and the observations made on the
HMS Beagle, Darwin put together his theory of
Natural Selection
Heritable
Genetic
Variation
+
Overproduction
=
Reproductive
Advantage
Original
Population
New Population
Descent with Modification
Ch.15 – Evolution
15.1 – Darwin’s Theory of Natural Selection
Survival of the Fittest
An adaptation is any characteristic that
increases fitness, which is defined as the ability
to survive and to produce fertile offspring
Living things adapt to their environment
Genetic
Variation
+
Overproduction
=
Reproductive
Advantage
Original
Population
New Population
Descent with Modification
Ch.15 – Evolution
Evidence for Evolution
The Fossil Record
Comparative Anatomy
Comparative Embryology
Comparative
Biochemistry
15.2 - Evidence for Evolution
The Darwinian view of
life predicts that
evolutionary transitions
should leave signs in
the fossil record
Paleontologists have
discovered fossils of
many such transitional
forms
Ch.15 – Evolution
The Fossil Record
15.2 - Evidence for Evolution
The Darwinian view of
life predicts that
evolutionary transitions
should leave signs in
the fossil record
Paleontologists have
discovered fossils of
many such transitional
forms
Ch.15 – Evolution
Comparative Anatomy
15.2 - Evidence for Evolution
Most animals show
similarities in internal
structure
Homologous
Structures
Vestigial
Structures
Similar structure – different use
Structures with reduced
function (“leftover parts”)
Ch.15 – Evolution
15.2 - Evidence for Evolution
Comparative Embryology Vertebrate embryos exhibit
homologous structures
during certain phases of
development
Ch.15 – Evolution
15.2 - Evidence for Evolution
Insert info about biological
resistance…visualizing evolution…
Ch.15 – Evolution
Comparative
Biochemistry
15.2 - Evidence for Evolution
Many organisms share
complex biomolecules.
The more closely related
the more similar the
molecules
1. How does the concept of
“descent with modification”
explain both the unity and
diversity of life?
2. Explain how overreproduction and heritable
variation relate to evolution by
natural selection
3. If you found a fossil of a
mammal that lived high in the
Andes, would you predict that it
would more closely resemble
present –day mammals from
South American jungles or
present –day mammals that
live high in Asian mountains?
Explain.
Have you been
paying attention?
4. Increased UV irradiation causes
the skin of humans to become
more darkly pigmented over a
period of days. The notion that the
offspring of such tanned
individuals should consequently
inherit darkened skin from their
parents is consistent with the ideas
of whom?
5. Most species of whale have 5
phalange (finger bones)
supporting their flippers. Why
would a whale have fingers?
What would you call those
phalange?
Ch.15 – Evolution
15.3 – Shaping Evolutionary Theory
Macroevolution
Population Genetics
Natural selection works on individuals
but only populations evolve
Evolution is the change of the allelic frequency in a population
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20 bugs
40 alleles for color
(incompletely dominant)
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B – 12/40 = .30 Bb
b - 28/40 = .70
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Bb
B – 18/40 = .45
b - 22/40 = .55
Over Time
Ch.15 – Evolution
15.3 – Shaping Evolutionary Theory
Populations evolve due to three main causes:
Natural Selection – Genetic Drift – Gene Flow
Natural Selection alters populations in one of three ways
Original
Population
Distribution
Disruptive
Selection
Stabilizing
Selection
Directional Selection
The average is selected for
Both extremes are selected for
One Extreme is selected for
Ch.15 – Evolution
15.3 – Shaping Evolutionary Theory
Populations
evolve
due tochanges
three main
Genetic Drift
is random
in a causes:
gene pool
Natural
Selection
– Genetic
Drift – Gene Flow
usually due
to independent
assortment
Usually only occurs in small populations
2 Examples
Founder Effect
Bottleneck Effect
A small sample of the population relocates
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Ch.15 – Evolution
15.3 – Shaping Evolutionary Theory
Populations
evolve
due to three
main causes:
Gene Flow is
the exchange
of genes
between
Natural
Selection
– Genetic Drift – Gene Flow
populations
from migration
Ch.15 – Evolution
15.3 – Shaping Evolutionary Theory
Populations can also evolve due to
nonrandom mating and mutations
Therefore, according to the Hardy-Weinberg Principle
A population in genetic equilibrium must meet 5
conditions:
No Genetic Drift
No Gene Flow
No Mutation
Random Mating
No Natural Selection
Ch.15 – Evolution
15.3 – Shaping Evolutionary Theory
Speciation
New species arise because of reproductive isolation
Reproductive isolation either occurs
with a physical barrier or without a physical barrier
Sympatric
Allopatric
Speciation Animation
Ch.15 – Evolution
15.3 – Shaping Evolutionary Theory
There are two hypothesis as to how
different species come to exist
Gradualism
Punctuated
Equilibrium
Changes occur
little by little
Changes occur rapidly
between periods of little
change
Ch.15 – Evolution
15.3 – Shaping Evolutionary Theory
Patterns of Evolution
Divergent Evolution
Convergent Evolution
or Adaptive Radiation
Organisms not
closely related evolve
similar traits
Many species arise from
one original species
Ch.15 – Evolution
15.3 – Shaping Evolutionary Theory
Patterns of Evolution
Coevolution
Many species evolve in close relationship with other species